Paladin of Tyranny 14/Hexblade 4/Bard 1/Warrior Skald 1.
Feats: Devoted Performer, Power Attack, Cleave, Doomspeak
Max out Intimidate.
Doomspeak is the key here. The DC is keyed off of charisma and uses FULL CHARACTER level. Adding Devoted Performer lets you do this 16 times per day (once for bard 1, once for warrior skald 1, 14 times for paladin 14). Warrior skald lets you add pretty much all other bardic music abilities you're missing from multiclassing out.
Penalties:
Aura of Despair: -2 to saving throws
Dark Companion: -2 to AC and saving throws
Doomspeak: -10 to attack rolls, saves, ability checks, and skill checks
Intimidate: -2 attack rolls, ability checks, saving throws
-16 to saving throws. -12 to attack rolls and ability checks. -10 to skill checks. -2 to AC.
With saves this low, you could probably chance a hexblade curse for an additional -2 to most of those as well.
Alternatively, you can add in dirgesinger 1, which if I remember correctly will let you tack on another -2 to saves. But this comes at the price of a feat, Requiem. The good news about that is you can now affect undead with bardic music abilities. You can take intimidating strike, daunting presence, frightful presence or whatever else to increase fear. Skill Focus (Intimidate) for all I care. However, this build is pretty much a niche. With 19 BAB and 18d10+2d6 HP, you'll be a front liner and that's where you will need to be too.
Tell your party casters they're welcome.
Comments, criticisms?